<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        <input type="text" v-model='toString'/>
        <span>{{toString}}</span>
        <button @click='toUpp'>转大写</button>
    </div>

    <script src="js/vue.js"></script>
    <script>

        let app = new Vue({
            el:'#app',
            data:{
                toString:''
            },
            methods:{
                toUpp(){
                    this.toString = this.toString.toUpperCase();
                }
            }
        });
    </script>
</body>
</html>